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Subject: Gun Caliber
technoid    7/20/2004 9:48:12 AM
Here's another question that probably shows my ignorance in the subject of large guns but I noticed in looking at web sites for large cannons that the term "caliber" is used differently for large guns. In the realm of small arms "caliber" is the bullet or bore size. When talking large guns it appears the term "caliber" refers to barrel length. Why is this different and how did it come about? In small arms the barrel length is simply refered to in units of length like "inches".
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scholar    RE:Gun Caliber   7/20/2004 3:06:45 PM
I think you're wrong about this. Calibre is calibre. On the other hand, I'm at least as ignorant as you, so hopefully one of the gunners will chime in.
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IsoT    RE:Gun Caliber   7/20/2004 5:11:12 PM
Well calibers in big guns measn how many caliber lenghts the tube is. (tube is the barrel of gun) Roughly, longer the tube, higher muzzle velocity. (well, upto some point.) well the tank gun is say 44 cals long menas the tube is 120mmx44=5280mm so 120mm gunbarrel is bit over 5 metres long (5 metres 28 centimetres).
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scholar    RE:Gun Caliber   7/20/2004 5:21:04 PM
MEaning how many times the calibre of the shell?
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Steve    RE:Gun Caliber   7/21/2004 12:55:48 PM
The above is correct and there is no reason not to give the barrel length of small arms in multiples or bore diameter (caliber), it’s just not common. There is another confusing nomenclature out there I saw questioned in another post. You frequently see a weapon designated as 40L70 ie. 40mm bore with a barrel 70x40mm (2.8m) long. The confusion comes from the brits who use L to designate Land, the much the same way the US uses M or the Canadians C. So the Challenger 1’s gun was the L11 and the Chally2’s the L30 but both were on the order of 120L40to50.
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scholar    RE:Gun Caliber   7/21/2004 1:22:24 PM
I miss the old days when one spoke of ammo weight. Six-pounders, etc.
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doggtag    RE:Gun Caliber and ammo weight   7/21/2004 10:26:22 PM
yes, but... there again is a problem: majority of 155mm guns fire "nominally" sized projectiles about 50kg. But when you look at just how many varied shells there are for each gun diameter, saying a gun fires a 35pound shell doesn't really tell you if its a 120mm tungsten sabot round (as opposed to a 40-odd pound DU round), or a 105mm artillery gun HE round. In WW2, there was the British 2pdr AT gun (of 40mm bore diameter). But the DU shells for the A-10's GAU-8 (of 30mm bore diameter) each weigh about 2 lbs also. Measuring guns by the weight of shell they threw met a dead-end when everyone found out just what kind and weight of "stuff" can be packed into "shells", as opposed to the old solid shot that was the determining factor of the "poundage" of a gun..
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technoid    RE:Gun Caliber and ammo weight   7/28/2004 12:17:31 PM
So back to my original question. What came first, the small arms terminology where "caliber" means bore size, or the large gun terminology where "caliber" means barrel length? And why do the two schools differ in the meaning? And where does he distinction change, when you get up to anything bigger than a 50 caliber bullet do we start using the term differently? I'm just curious and always want to learn.
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IsoT    RE:Gun Caliber and ammo weight   8/6/2004 4:08:32 PM
Weren't the ammo weight thing the same as with shotgus still today. Meaning 12 bore shotgun means the bore is the size of lead speher of which 12 goes for pound. Hence twopounder would meant it takes two that size speher for a pound. Made sence when your artillery round was a sphere, but now as the rounds might be even five times the bore diameter isn't really informative. And dont even start from the shotsize. Havent got a clue how they go.
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wagner95696    RE:Gun Caliber and ammo weight   8/7/2004 3:18:53 PM
Caliber means bore size. Barrel length is correctly expressed as 'calibers', plural. For example, L/55 means the barrel is 55 calibers long, or 55 times the caliber. Caliber [bore size, e.g. 155mm] is an actual measurement wheras 'calibers', plural is a ratio [55:1] and independent of any specific measurement. The problem is that over the years people got sloppy with their grammar and dropped the 's' from 'calibers', thus causing the confusion.
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technoid    RE:Gun Caliber and ammo weight   8/11/2004 4:45:12 PM
A friend just suggested that perhaps the term "caliber" denoting bore size is a U.S. or English term. Perhaps the term "calibers" denoting tube length is a French term. Many gun terms originated in French. Anyone know if there is a French term that might be translated "calibers" and what it means?
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